The present invention relates to a storage device which can be optimized for metal bar cropping lines.
It is known that lines for cropping metal bars meant to constitute the reinforcement frames of reinforced-concrete structures and the like are used in the field of building. These so-called "fixed" cropping lines generally have means for feeding the metal bars to a cropping station provided with locator means adapted to adjust the length of the portions cropped from the bars; the feeder means take the bars to be cropped from a corresponding magazine and push them into abutment against the locator means, along a measuring unit generally provided with roller supporting means. Adapted cropping means then crop the bars to the preset size.
In other cases, no locator means are provided and the bars to be cropped are measured by means of wheels connected to encoder devices.
In performing the cropping operation, there is an economic requirement to minimize waste. In order to achieve this result, an electronic computer is normally used; according to the batches to be produced, the computer associates several sizes so as to approximate the total length of the bars to be cropped. The batches to be produced are in fact generally constituted by bars of different lengths according to the various intended uses.
It is thus known that it is necessary to arrange, to the side of the cropping line, storage devices adapted to separately collect the bars cropped according to the different sizes, so as to reconstitute the batches. In practice, the metal bars are cropped automatically into portions having different lengths, which correspond to the required sizes; these portions are then conveyed to respective storage areas. This step is usually defined "cropping optimization".
Simpler cropping lines usually have two storage areas, arranged respectively on either side of the line. The storage areas have respective fixed comb-shaped devices, often four on the left and four on the right, generally one whereof is adapted to receive the bars which will remain straight and the other one is adapted to receive the bars to be shaped, which are then conveyed to bending benches. Each one of the comb-shaped devices forms a plurality of stores meant to receive respective groups of bars cropped to the different intended sizes. Before being removed from the storage devices, the cropped bars are generally tied in bundles.
In order to move the cropped bars it is usually necessary to use a crane. This is a considerable drawback, especially as regards the bars to be conveyed to the bending benches.
In order to overcome this drawback, i.e., to avoid the use of cranes, it has been suggested to use a storage device constituted by a large truck movable along rails arranged transversely below the cropping line. The truck is adapted to receive the cropped bars and to sort them directly to the bending benches; for this purpose, the truck is provided with a plurality of roller conveyors, usually four, meant to receive the different batches of bars to be kept straight or to be shaped.
In addition to allowing a smaller number of stores and therefore reduced cropping optimization, this solution entails a higher cost. The fact is also objected that both the bars to be kept straight and the bars to be shaped are collected on the truck, and this is a cause of potential confusion. Moreover, the presence of a movable element is a risk factor with respect to the system safety.
Another solution which has been suggested in order to obviate the above-mentioned drawbacks consists in laterally sorting the bars to be shaped to a chain conveyor which directly feeds a bending bench arranged to the side of the cropping line. In practice, the cropped bars to be bent fall laterally onto the chains, which are actuated along planes lying transversely to the cropping line and provided with teeth which form appropriate compartments, the bars being then conveyed to the bending bench.
This solution allows to reduce the system bulk and to avoid the risks connected to moving parts, but it does not allow true cropping optimization. The device in fact has a single store which can be selected, i.e., which is available to divide the different batches of bars, and it is therefore impossible to separate the bars after cropping. Accordingly, the most important characteristic distinguishing cropping lines, i.e., optimization, is set aside.